Simply Charlotte Mason has a great resource that I discovered just a few weeks ago: Your Business Math Series. The concept is basic. Use your math skills to run a business - you know, like real life! A Pet, Sport or Bookstore are the options offered and Samuel chose to own bookstore.
This week he is just starting up his business by creating a logo (pictured above) and for the last three days he has been working on the initial inventory, which is really tedious work. How do you know how many "Trumpet of the Swan" books you will need? Then he has to multiply each order by the quantity and THEN add up the total of his order. Add, multiply, add, multiply, add, multiply. No calculator...well, I did let him use the calculator to double check his answers, which, by the way, were all correct.
Armed with $10,000 (of imaginary money) he will be working on filling orders, preparing ledger entries, calculating sales tax, adjusting inventory amounts, paying bills, advertising, and figuring out profit/loss for each month. Three days a week he will work on Math 5 (Teaching Textbooks) and Timez Attack (for multiplication) and one day will be dedicated to his business Samuel's Books.